GASOLINE PARTICULATE FILTER

Abstract

The present invention provides a particulate filter for use in an emission treatment system of a gasoline engine, the filter having an inlet side and an outlet side, wherein at least the inlet side is loaded with a synthetic ash.

Claims

1. A particulate filter for use in an emission treatment system of a gasoline engine, the filter having an inlet side and an outlet side, wherein at least the inlet side is loaded with a synthetic ash.

2. The particulate filter of claim 1, wherein the particulate filter is a wall-flow filter.

3. The particulate filter of claim 1, wherein the synthetic ash comprises one or more of: aluminium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, cerium zirconium (mixed) oxide, zirconium oxide, cerium oxide and hydrated alumina.

4. The particulate filter of claim 3, wherein the synthetic ash comprises one or more of: zinc oxide, zinc carbonate, calcium oxide, calcium carbonate and zirconium oxide.

5. The particulate filter of claim 1, wherein the synthetic ash is devoid of platinum group metal-containing catalytic material and/or devoid of catalyst-poisoning materials.

6. The particulate filter of claim 5, wherein the catalyst poisoning materials in the synthetic ash is substantially free of sulphur oxides, phosphorus, magnesium, manganese, and lead.

7. The particulate filter of claim 1, wherein the filter comprises from 1 to 50 g/L of the synthetic ash, preferably from 5 to 40 g/L, more preferably from 10 to 35 g/L, still even more preferably from 15 to 35 g/L, yet even more preferably from 20 to 30 g/L.

8. The particulate filter of claim 1, wherein the filter comprises a porous body comprising a plurality of pores, and further comprising one or more catalytic washcoats within at least a portion of the plurality of pores, wherein the one or more washcoats preferably include a TWC washcoat.

9. The particulate filter of claim 1, wherein the particulate filter is uncanned.

10. An emission treatment system comprising the particulate filter of claim 1, wherein the inlet side of the particulate filter is arranged to be upstream of the outlet side.

11. A method of producing a particulate filter for use in an emission treatment system of a gasoline engine, the method comprising: providing a filter having an inlet side and an outlet side; and loading at least the inlet side with a synthetic ash.

12. The method of claim 11, wherein the particulate filter is according to claim 1.

13. The method according to claim 11, wherein the method further comprises canning the synthetic ash-loaded filter.

14. The method according to claim 11, wherein the synthetic ash is loaded in the form of a particulate having a D90 of less than 1 m.

15. The method according to claim 11, wherein loading at least the inlet side with the synthetic ash comprises: contacting the inlet side with the synthetic ash; and providing a gaseous flow from the inlet side to the outlet side and/or a vacuum from the outlet side to compact the synthetic ash against the filter.

16. The method of claim 15, wherein the inlet side is contacted with the synthetic ash in the form of either a gaseous suspension or a liquid suspension.

17. The method of claim 11, further comprising calcining the loaded synthetic ash.

18. Use of a synthetic ash loading to increase the fresh filtration efficiency of a filter for use in an emission treatment system of a gasoline engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The invention will now be described in relation to the following non-limiting figures, in which:

[0051] FIG. 1A is a perspective view that schematically shows a particulate filter 1 according to an embodiment of the present invention.

[0052] FIG. 1B is an A-A line cross-sectional view of the particulate filter 1 shown in FIG. 1A.

[0053] FIG. 2 shows a schematic diagram of an emission treatment system for a gasoline engine.

[0054] FIG. 3 shows X-ray images of particulate filters according to embodiments of the present invention.

[0055] FIG. 4 shows a plot of backpressure characteristics of particulate filters according to embodiments of the present invention and a prior art particulate filter.

[0056] FIG. 5 shows a plot of filtration efficiencies of a particulate filter according to an embodiment of the present invention and a prior art particulate filter.

[0057] FIG. 6 shows X-ray images of particulate filters: Comparative Filter III and Filter IV according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0058] A particulate filter 1 according to an embodiment of the present invention is shown in FIG. 1A and FIG. 1B. In this embodiment, the particulate filter is a wall flow filter. It includes a large number of channels arranged in parallel with each other in the longitudinal direction (shown by a double-sided arrow a in FIG. 1A) of the filter 1. The large number of channels includes a first subset of channels 5 and a second subset of channels 10.

[0059] The channels are depicted such that the second subset of channels 10 is narrower than the first subset of channels 5. However, the channels may alternatively be substantially the same size.

[0060] The first subset of channels 5 is open at an end portion on a first end face 15 of the wall flow monolith 1 and is sealed with a sealing material 20 at an end portion on a second end face 25.

[0061] On the other hand, the second subset of channels 10 is open at an end portion on the second end face 25 of the wall flow monolith 1 and is sealed with a sealing material 20 at an end portion on the first end face 15.

[0062] The filter 1 may be provided with a catalytic material within pores of the channels walls 35. The catalyst supported in the channel wall 35 of the monolith 1 functions as a catalyst for treating the exhaust fumes.

[0063] Synthetic ash 50 is situated within the first subset of channels 5 and is packed against the sealing material 20 at the end portion on the second face 25. The packed bed of synthetic ash extends from the sealing material along the channel walls 35.

[0064] Therefore, when the particulate filter is used in an exhaust system, exhaust gases G (in FIG. 1B G indicates exhaust gases and the arrow indicates a flowing direction of exhaust gases) introduced to the first subset of channels 5 will pass through the synthetic ash 50 and the channel wall 35 interposed between the channel 5a and the channels 10a and 10b, and then flow out from the monolith 1. Accordingly, particulate matter in exhaust gases is captured by the synthetic ash 50.

[0065] In the embodiment of the emission treatment system 100 shown in FIG. 2 the flow of exhaust gas 110 passes through the particulate filter 1. The exhaust gas 110 is passed from the gasoline engine 115 through ducting 120 to the exhaust system 125.

[0066] It should be noted that the particulate filter is described herein as a single component. Nonetheless, when forming an emission treatment system, the filter used may be formed by adhering together a plurality of channels or by adhering together a plurality of smaller filters as described herein. Such techniques are well known in the art, as well as suitable casings and configurations of the emission treatment system.

[0067] The catalytic wall-flow monolith will now be described further in relation to the following non-limiting example.

Example 1

[0068] Filter I: a particulate filter was prepared by loading ZnO powder into the inlet side of a commercial 300/8 65% porosity uncoated cordierite wall flow filter. The ZnO power was placed onto a supporting mesh above the inlet of the filter to be coated and an air stream was directed from the inlet side through the wall flow filter and out of the outlet side, thereby drawing the ZnO power through the mesh and into the filter, compacting the ZnO powder against the sealing plugs of the inlet channels. Approximately 45 g of ZnO powder was loaded onto the filter, providing a loading level of approximately 25 g/L.

[0069] Filter II: a second particulate filter was prepared in a similar manner as in Filter I, but with Disperal powder (a high purity dispersible alumina hydrate) used instead of ZnO.

[0070] Filter III (Comparative): another particulate filter was prepared by coating a commercial 300/8 65% porosity uncoated cordierite wall flow filter with TWC washcoat (0.4 g/in.sup.3 washcoat loading, 30 g/ft.sup.3 PGM, (0:27:3, Pt/Pd/Rh)) from the inlet and outlet side.

[0071] Filter IV: another particulate filter was prepared first as in Filter III, by coating a commercial 300/8 65% porosity uncoated cordierite wall flow filter with TWC washcoat (0.4 g/in.sup.3 washcoat loading, 30 g/ft.sup.3 PGM (0:27:3, Pt/Pd/Rh)) from the inlet and outlet side and calcining at 500 C. before 45 g of Disperal powder was loaded into the inlet side of the coated filter, prepared in a similar manner as in Filters I and II.

[0072] X-ray images of Filters I and II are shown in FIG. 3 [top: Filter II (Disperal); bottom: Filter I (ZnO)], with the inlet sides being at the top of the images. The dark bands indicate the plugs A at the top and bottom of the filters. Additional dark shading at the bottom of the filters corresponds to synthetic ash B compacted against the end plugs of the channels.

[0073] Back pressure characteristics of the particulate filters were investigated, both before and after calcining at 500 C., and the results are shown in FIG. 4 together with the results of a wall flow filter containing no synthetic ash (curves from top to bottom: Disperal, not calcined (Filter II); Disperal, calcined (Filter IIC); ZnO, not calcined (Filter I); ZnO-calcined (Filter IC); and uncoated (dashed)). It can be seen that the filters loaded with synthetic ash, particularly after calcining, exhibited similar back pressure characteristics to a filter in which no synthetic ash had been loaded.

[0074] The fresh filtration efficiencies of Filter I and an uncoated particulate filter in which no synthetic ash was loaded were measured with a TWC in the first position (1 L volume substrate with 400/4 CPSI and a catalyst coating with 21 g/ft.sup.3 (0:18:3. Pt/Pd/Rh) (Euro 5 compliant 2 L gasoline direct injection engine; NEDC testing; PN engine out=1.2810.sup.12), and the results are shown in FIG. 5. It can be seen that the fresh filtration efficiency of the ZnO-loaded particulate filter (right hand side) was 91%, whereas the particulate filter without synthetic ash exhibited a fresh filtration efficiency of 73%. The results indicate that the particulate filter of the present invention provides an advantageous combination of high fresh filtration and low back pressure.

[0075] Similar to FIG. 3, X-ray images of Filters III and IV are shown in FIG. 6 (top: Comparative Filter III; bottom: Filter IV), with the inlet sides being at the top of the images.

[0076] Although preferred embodiments of the invention have been described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the scope of the invention or of the appended claims.

[0077] For the avoidance of doubt, the entire contents of all documents cited herein are incorporated herein by reference.